In current Code Division Multiple Access (CDMA) communication systems a Radio Link Protocol (RLP) is utilized for the link layer to transport data traffic between a mobile unit and infrastructure equipment. During typical data transmission Point to Point Protocol (PPP) is utilized on top of the RLP. In such situations, RLP fragments PPP packets into 20 millisecond frames that are transmitted over the air. This is illustrated in FIG. 1. As shown, PPP packets 101 are segmented into RLP frames 102 and transmitted over the air.
RLP is a Negative-Acknowledgment (NAK) based protocol in that the receiver does not acknowledge correctly-received RLP frames. RLP only requests the retransmission of RLP frames that were incorrectly received by sending a NAK to the transmitter. Prior to receiving the NAKed frame, subsequently transmitted RLP frames continue to be received. After a predetermined number of NAKs being sent for a particular frame, and if the frame has not been received, the receiver aborts the NAK procedure and passes the incorrectly received RLP frames to the higher layer (PPP).
From the upper-layer's perspective, aborting a frame at the RLP layer is equivalent to aborting the entire PPP packet. This is because PPP reassembles all RLP frames for the PPP packet, and then performs a checksum match for the entire PPP packet. Since the PPP packet contains an errored RLP frame (on account of the RLP abort), the checksum match will fail. A checksum failure results in a PPP packet discard. Thus, even a single aborted RLP frame results in the eventual discard of the upper-layer PPP packet that the aborted RLP frame resides.
Since RLP is octet-based as opposed to packet based, the receiver is unaware of higher layer (PPP) framing. Thus, RLP continues to reliably deliver subsequent frames belonging to the PPP packet even after having aborted on a frame corresponding to the packet. In other words, RLP continues to request retransmission of frames (through NAKs) corresponding to a particular PPP packet, even though PPP will eventually discard the entire PPP packet. The obvious inefficiencies of this approach is that RLP frames belonging to the same PPP packet as the aborted RLP frame are unnecessarily retransmitted. In other words, RLP attempts to deliver RLP frames error-free to the upper layer when they will be discarded nonetheless. Additionally, subsequent PPP packets are unnecessarily delayed in this current RLP process. Therefore, a need exists for a method and apparatus for data re-transmission within a communication system that does not unnecessarily retransmit RLP frames.